# A farmer stores bales of hay outdoors over winter. By spring, the bales that were left uncovered and in contact with the wet ground have largely decomposed, whereas bales stored on raised wooden pallets under a waterproof cover remain intact. Explain why the uncovered bales decomposed much faster than the covered bales.

> Pearson Edexcel A-Level Biology A (9BI0) — 5.5 Decomposition and decay · Explain · 5 marks

> Hay bales are made of dried grass. Decomposers such as bacteria and fungi break down organic material by secreting enzymes onto it and absorbing the products.

## Mark scheme (5 marks)

1. Decomposers (bacteria and fungi) are responsible for breaking down the organic material in the hay
2. The uncovered bales were wet / moist, providing the water needed for decomposer activity
3. Decomposers secrete enzymes onto the hay and absorb the soluble products (extracellular digestion)
4. The covered bales were kept dry, so decomposer activity was greatly reduced
5. Raising the bales on pallets also reduced contact with soil microorganisms / prevented waterlogging, further limiting decomposition

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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